In recent years, the capacity of wind power common coupling system grows continually and rapidly. Accordingly, problems about the voltage in large-scale wind power integration areas occur. If wind energy resources are far away from load centers, the wind power will be coupled into weak parts of the power system lacking of the support of regular water or thermal power plants, so regional voltages in these parts are easily affected by active and reactive powers of the wind farm. When the wind gusts, the wind power may fluctuate significantly in a minute, thereby resulting in a drastic fluctuation of the voltage at a point of common coupling.
Currently, in wind farms put into operation in the worksite, voltage controllers are mostly designed with reference to conventional thermal power plants, i.e. wind turbines and SVCs/SVGs (Static Var Compensators/Static Var Generators) are viewed as different reactive power sources and less consideration is took on differences of response characteristics thereof. Conventional control methods give priority to a current state optimization but ignore influences on a future state of the system during the reactive power adjusting process of the wind turbines and the SVCs/SVGs. In order to avoid voltage oscillations due to the mismatching between the reactive power adjustment and a system state at the time when the adjustment is completed, a smaller reactive power adjusting step length is set and the voltages are controlled by a way of multistep approaching during the controlling process. When the wind fluctuates rapidly, in the case that the reactive power adjustments of the wind turbines are limited, the SVCs/SVGs track voltage targets, such that their own dynamic reactive power reserves are exhausted firstly, and then a problem that no support can be provided in the case of emergency or voltage fluctuating drastically in future is brought.